Currently-available pre-collision warning/detection systems do not distinguish between two vehicles which are about the same size but which have significantly different mass and hence have critically different collision characteristics. Consequently, such pre-collision warning/detection systems are limited to (1) pre-arming of non-resettable devices, such as airbags, so that they can be deployed more rapidly in cases where the potential subsequent collision is sufficiently severe to warrant deployment, and (2) triggering non-aggressive resettable safety devices that do not interfere with the vehicle driving function, such as extendible/retractable bumpers and extendible/retractable knee bolster systems. There is a need for pre-collision warning/detection systems which not only give warning of an imminent or nearly imminent potential collision but also predict the severity of the potential collision.